In the conventional preparation of semiconductors a predetermined amount of extremely pure metal phosphide or arsenide are laid down on the substrate crystal. The accepted mode of carrying out this process is to charge predetermined amounts of phosphine or arsine into a stream of hydrogen together with the appropriate amount of an organometallic compound. The said mixed gas stream is passed through a furnace at a predetermined temperature, said furnace containing the crystal on which deposition is desired. At the predetermined temperature, an elimination reaction will take place whereby the organic portion of the organometallic is eliminated and replaced by phosphorus or arsenic as is appropriate. In order for this reaction to take place properly and efficiently the organometallic utilized must be sufficiently stable under the furnace conditions that it does not decompose per se and yet it must be sufficiently reactive to permit the elimination reaction to occur substantially instantaneously when the gas stream enters the heated furnace area.
The organometallic should also be comparatively simple to prepare and, desirably, not be pyrophoric. That is to say, that should it accidently come into contact with air due to process errors, it would not spontaneously inflame.
Heretofore, the organic group used in the synthesis of these compounds has been the methyl group. However, the metalomethyls of this group are extremely volatile and pyrophoric. This handling disadvantage makes it desirable to provide alternative compounds.
The ethyl, isopropyl and isobutyl derivatives decompose too readily at elevated temperatures to permit the elimination reaction to take place in the proper manner.
In my copending application there are provided the trisneopentyl derivatives of gallium and indium. These have greater thermal stability and longer shelf life than other metalo-organic compounds of these metals. They are easier to prepare at lower cost of synthesis than the previously known compounds and moreover, lack pyrophoric character.
Furthermore, these compounds have a sufficient level of volatility to permit them to be utilized in the gas phase synthesis of the corresponding phosphides or arsenides, a procedure which is useful in the manufacture of various semiconductors containing the said phosphides and arsenides.